As a hot-spot research subject in today's communication standardization field, NGN (Next Generation Network) adopts packet technologies including IP (Internet Protocol), etc, as the carrier network technology to converge fixed communication and mobile communication. NGN can provide more abundant multimedia services, including emerging services with real time requirements such as VoIP (Voice over IP), video conferencing, remote multimedia teaching and video on demand, etc, these services require the communication network to provide highly efficient end-to-end Quality of Service support; at the same time, users' requirements on the network Quality of Service (QoS) are also becoming increasingly demanding. Therefore, how to provide end-to-end QoS may be one of the core issues in NGN.
The ITU-T (International Telecommunication Union-Telecom) has proposed RACF (Resource and Admission Control Functions) to solve QoS problems in NGN carrier networks. The latest draft of RACF that ITU-T announced in April 2007 offers a functional architecture for RACF, as shown in FIG. 1. The RACF is comprised of two parts: a Policy Decision Functional Entity (PD-FE) and a Transport Resource Control Functional Entity (TRC-FE).
The PD-FE is independent of the transmission technology, and is also independent of Service Control Functions (SCF). The PD-FE makes a final decision for network resource and admission control based on the network policy rules, the service information provided by the SCF, the transport layer subscription information provided by Network Attachment Control Functions (NACF) as well as the resource and admission decision result provided by TRC-FE. The PD-FE performs gate control on the PE-FE based on each stream, and utilizes the policy rules based on services.
The TRC-FE is independent of services, but is dependent on the transmission technology. The TRC-FE is responsible for collecting and maintaining the topology and resource status information of the transport network, controlling the utilization of the resource based on topology, connectivity, the availability of network and node resource, as well as network information such as transport layer subscription information in the access network, and performing admission control for the transport network. Through the Rt reference point, the PD-FE requests the TRC-FE to detect or decide the QoS resource on the requested media flow path.
The transport functional entity is comprised of a Policy Enforcement Functional Entity (PE-FE) and a Transport Resource Enforcement Functional Entity (TRE-FE). The PE-FE is a packet-to-packet gateway which can be located between a Customer Premises Equipment (CPE) and the access network, between the access network and the core network or between networks of different operators, and is the key node to support dynamic QoS control, port address translation control and Network Address Translator (NAT) traversing.
The PD-FE is the policy decision functional entity which may make a preliminary QoS resource decision based on the media flow session information (acquired from SCF through the Rs interface) and user's transport resource subscription information (acquired from NACF through the Ru interface), then interact with the TRC-FE to confirm whether there are sufficient QoS resource, make a final decision, and passes the decision down to PE-FE for enforcement.
The TRC-FE is mainly responsible for resource control, which monitors the resource in the network and collects related information, and responds according to the specific resource conditions when the PD-FE requests resource.
The PE-FE performs policy control (gate control, bandwidth, traffic flow classification and tagging, traffic flow shaping, Layer 2 and Layer 3 QoS mapping, and collecting and reporting resource utilization information, etc) primarily under the direction of the PD-FE.
According to the current description of the TRE-FE protocol, Layer 2 policy enforcement is performed under the direction of the TRC-FE, but neither the specific function nor the scope has been determined.
The resource and admission control system supports the QoS resource control in two modes which are “PULL” mode and “PUSH” mode, in order to adapt to different types of CPEs or Customer Premises Networks (CPNs).
Under the PUSH mode, the SCF requests QoS resource authorization and resource reservation from the resource and admission control system for the service initiated by the Customer Premises Equipment; if the request could be satisfied, the resource and admission control system may actively push the decision to the transport function in order to obtain the corresponding transport resource.
Under the PULL mode, the SCF requests QoS resource authorization and resource reservation from the resource and admission control system for the service initiated by the Customer Premises Equipment; and upon receiving the transport layer signaling message, the transport function may actively request a decision from the resource and admission control system.
The PULL mode is further divided into two types of resource and admission control:
one type requires authorization; the resource and admission control process of this type includes three processes which are Authorization, Reservation and Commitment, where the latter two processes can typically be combined into a single process; authorization is initiated by the CPE and activated by the SCF to generate a request; while Reservation and Commitment are initiated by the CPE and activated by the transport function to generate a resource request;
with the other type, the resource and admission control system configures fixed services for a Customer Premises Equipment with a specific IP address; the resource and admission control process of this type requires no authorization, and the Customer Premises Equipment directly initiates a resource reservation request.
FIGS. 2 and 3 show the flowcharts of the resource and admission control process in the RACF PULL mode that requires no authorization; in the resource and admission control that does require the authorization, before Step 201 or Step 301, the Customer Premises Equipment may still need to first initiate an authorization request to the RACF in order to obtain the authorization; after providing such authorization for the request, the PD-FE may notify the TRC-FE and the PE-FE, and the TRC-FE or the PE-FE may store PD-FE Identifier.
FIG. 2 shows the resource and admission control process activated by the TRE-FE, which includes the following steps:
201, the CPE directly requests resources from the TRE-FE through a path-coupled transport layer signaling message;
the resource request initiated by the CPE may activate the TRE-FE to send a resource request message;
202, the TRE-FE TRC FE sends the resource request message to the TRC-FE;
203, TRC-FE checks the resource request according to the current resource conditions and, if the request is valid, sends a resource decision request message to PD-FE.
FIG. 3 shows the resource and admission control process in the PULL mode activated by the PE-FE, which includes the following steps:
301, the CPE directly requests resources from the PE-FE through a path-coupled transport layer signaling message;
the resource request initiated by the CPE may activate the PE-FE to send a resource decision request message;
302, the PE-FE sends the resource decision request message to the PD-FE.
As shown in FIG. 4, the TRC-FE or the PE-FE has to select the exact PD-FE in Step 203 and Step 302 because the TRC-FE or the PE-FE may interact with multiple PD-FEs. Therefore, for the PULL mode that requires authorization, the exact PD-FE refers to the very PD-FE that authorizes the Customer Premises Equipment during the authorization process; for the PULL mode that requires no authorization, the exact PD-FE refers to the very PD-FE to which the static configuration corresponds. The problem existing in the prior art is that the TRC-FE or the PE-FE can not select the exact PD-FE to implement the resource reservation request process.